Holder for conductive contact

ABSTRACT

A holder supported by an arm comprises a metallic reinforcing member and a plastic holder hole forming member filled in an opening formed in the reinforcing member. Holder holes are formed in the holder hole forming member, and a coil spring and electroconductive needle members are installed in each holder hole to thereby provide a contact probe having two moveable ends. Because the holder is essentially made of the metallic member, the mechanical strength of the holder can be improved over that formed strictly from plastic material. Therefore, the contact probe holder would not suffer from dimensional changes of the holder owing to aging compounded by temperature changes for testing (tests under high temperature conditions) and residual stress so that the change in the pitch of the holder holes can be avoided, and a high level of precision can be ensured. Therefore, the contact probe allows tests to be conducted in a stable manner over an extended period of time.

TECHNICAL FIELD

The present invention relates to an electroconductive contact probeholder that can be used for passing electric signals to and from printedcircuit boards, electronic devices or the like.

BACKGROUND OF THE INVENTION

Contact units that are used in contact probes for electrically testingconductive patterns of printed circuit boards and electronic devicesinclude those having a pair of needle members that are disposed so as tobe moveable in the axial direction on either axial end as disclosed inJapanese UM laid open publication No. 60-154868. Such anelectroconductive contact unit having two moveable ends is typicallyused for temporarily connecting, for testing purposes, two circuitboards that are eventually permanently connected in the final product.LCD panels and array circuit boards can be tested by using a contactprobe having a same number of contact units as the number of electrodesin the circuit pattern of the LCD panel. The testing of the LCD paneltypically takes place before the LCD panel is finally connected to a TABconsisting of a panel drive LSI and a printed circuit board.

As disclosed in Japanese patent application No. 06-87337 by the sameapplicant, an electroconductive contact probe holder can be formed bylaminating a plurality of insulating plastic plates one over another. Ineach contact unit of such a contact probe, electroconductive needlemembers are provided on either end of a compression coil spring, and aholder hole for receiving this assembly is formed by a hole passedacross the thickness of these insulating plates.

A specific example is illustrated in FIG. 9, small diameter holes 41 a,41 b, 42 a and 42 b are formed in upper and lower insulating members 41and 42, and large diameter holes 43 a and 43 b are formed inintermediate insulating members 43 laminated between the upper and lowerinsulating members 41 and 42 so that coil springs 44 and 45 are receivedin the corresponding large diameter holes 43 a and 43 b and the needleportions of the needle members 46, 47, 48 and 49 are supported by thecorresponding small diameter holes 41 a, 41 b, 42 a and 42 b. Eachneedle member 46-49 is provided with a flange portion adapted to bereceived in the corresponding large diameter hole 43 a or 43 b andengage a shoulder defined between the corresponding large diameter hole43 a or 43 b and small diameter hole 41 a, 41 b, 42 a or 42 b to preventthe corresponding needle member 46-49 from coming off.

These insulating members 41 to 43 jointly form a laminated assembly 50,and a plurality of contact units 51 each comprising a coil spring 44 anda pair of needle members 46 and 48 are arranged in this holder, thenumber of the contact units 51 corresponding to the number of theterminals of an LCD panel 53. The insulating members 41 to 43 may bejoined to each other by using threaded bolts or a bonding agent. In theillustrated example, each contact unit 51 is electrically connected toanother contact unit 52 consisting of a coil spring 45 and needlemembers 47 and 49 via a sheet portion 54 a of a TAB 54 provided on theupper surface of the upper insulating member 41, and the needle member49 of the contact unit 52 is in turn connected to an external testingdevice via a PCB 55 provided on the lower surface of the lowerinsulating member 42.

The holder 50 for the contact units each having two moveable ends isconstructed as described above, and includes holder holes consisting oflarge diameter holes 43 a and 43 b and small diameter holes 41 a, 41 b,42 a and 42 b. An arm 56 of an actuator supports the holder 50 via apart of the intermediate insulating member 43, for instance. In thecourse of a test, the arm 56 is moved and the needle members 48 areresiliently engaged with the terminals of the LCD panel 53.

However, according to this arrangement, because each of the insulatingmembers that form the holder consists of a single piece member made ofplastic material, dimensional errors may be produced in the holder overtime owing to the change in temperature during the test (test under ahigh temperature condition), residual stress produced by a machining orother working process and absorption of moisture. Such dimensionalerrors give rise to changes in the pitch between adjacent holder holesand the positional precision of the contact point of each contact unit(the position of the tip of the needle member) may be impaired.

BRIEF SUMMARY OF THE INVENTION

In view of such problems of the prior art, a primary object of thepresent invention is to provide a contact probe holder that can ensure ahigh level of positional precision to the contact points whilesimplifying the manufacturing process.

A second object of the present invention is to provide a contact probeholder that can be reduced in thickness without compromising themechanical strength thereof.

A third object of the present invention is to provide a contact probeholder that is favorable in terms of both electric and mechanicalproperties.

According to the present invention, at least most of the objects can beaccomplished by providing an electroconductive contact probe holder forsupporting a plurality of contact units for contacting an object,comprising: a base plate made of a first material and provided with anopening therein; and film made of a second material and deposited on asurface of the base plate so as to cover at least an innercircumferential surface of the opening; a holder hole forming membermade of a third material and filled in the opening substantially withoutextending outside the opening; a plurality of holder holes being passedacross a thickness of the holder hole forming member each for receivinga contact unit therein.

The first material may comprise a member selected from a groupconsisting of metallic material, semiconductor material, ceramicmaterial and glass material, and the second and third materials maycomprise a same or different plastic materials.

According to this arrangement, the support members of the holder may bemade from high strength material such as metallic material having a lowcoefficient of thermal expansion, and the dimensional changes owing tothe change in temperature during testing (tests under a high temperaturecondition) can be favorably controlled because the holder is in effectsubstantially entirely made of the high strength material as opposed toa holder entirely made from plastic material. Dimensional changes due toaging compounded by residual stress can be avoided. Therefore, even whenthe terminals of the chip or the like that are to be accessed aredensely arranged, an adequate level of positional precision can bemaintained in the pitch of the corresponding contact units withoutregard to the surrounding environment and the service period.

In particular, if film is formed on the inner circumferential surface ofthe opening to enhance a bonding force between the base plate and holderhole forming member, the force of attachment of the holder hole formingmember in the opening can be increased, and the integrity of the contactprobe can be improved. Even if the bonding force between the film andbase plate is not strong, by depositing the film substantially over theentire surface of the base plate, the film can be firmly attached to thebase plate, and the bonding force between the holder hole forming memberand base plate can be easily increased.

The film may be formed on the outer surface of the high strength baseplate and the inner circumferential surface of the opening, and materialsuitable for forming the holder holes may be laminated over the film.Thereby, the masking that would be necessary when material suitable forforming holder holes is simply filled into the opening is not required,and the work efficiency can be improved. If film consisting ofinsulating plastic material is coated over the surface of the baseplate, and the material suitable for forming holder holes that is placedover the film is electrically insulating, the overall insulatingproperty can be improved owing to the provision of the two layers ofinsulating material. Therefore, the thickness of the film and layer canbe reduced without impairing the insulating performance, and the reducedthickness of the film and layer allows the thickness of the holder to beminimized.

The material of the holder hole forming member may consist of plasticmaterial which produces relatively little static electricity, and atleast a surface of the high strength base plate that requires insulationmay be provided with insulating film. Thereby, when the electrostaticproperty is required to be considered owing to the highly densepopulation of the terminals of the chip or other object to be tested,the holder hole forming member may be made from plastic material havinga favorable electrostatic property as the insulating film makes up forthe deficiency the material of the holder hole forming member may havein electric insulation.

The high strength base plate may be provided with a threaded hole forjoining the holder with another member so that the mechanical strengthof the thread is increased as compared with that formed in a plasticmember, and the fastening force of the threaded bolts can be increased.Therefore, the holder can be firmly joined to the other member. Also,even if the holder is assembled and disassembled repeatedly, the threadwould not be damaged, and the maintenance of the contact probe isfacilitated.

According to a preferred embodiment of the present invention, anengagement feature is formed on an inner circumferential surface of theopening so that the force of attachment between the holder hole formingmember and base plate can be increased. According to a particularlypreferred embodiment of the present invention, the base plate is made ofa silicon wafer and an engagement feature comprises an inwardly directedridge formed by anisotropically etching the inner circumferentialsurface of the opening.

BRIEF DESCRIPTION OF THE DRAWINGS

Now the present invention is described in the following with referenceto the appended drawings, in which:

FIG. 1 is a schematic longitudinal sectional view of a holder for acontact probe embodying the present invention;

FIG. 2 is a sectional view taken along line II-II of FIG. 1;

FIG. 3 a is a fragmentary longitudinal sectional view of a secondembodiment of the present invention comprising a high strength baseplate formed with an opening;

FIG. 3 b is a view similar to FIG. 3 a showing the holder having aplastic layer formed over the high strength base plate;

FIG. 3 c is a view similar to FIG. 3 a showing the holder having aholder hole forming member placed in the opening;

FIG. 3 d is a view similar to FIG. 3 a showing the holder having holderholes formed in the holder hole forming member;

FIG. 4 a is a view similar to FIG. 3 a showing a holder given as a thirdembodiment comprising an opening provided with a ridge;

FIG. 4 b is a view similar to FIG. 4 a showing the holder having aholder hole forming member placed in the opening;

FIG. 5 is a view similar to FIG. 1 showing a fourth embodiment of thepresent invention;

FIG. 6 a is a perspective view showing a contact probe provided withhighly concentrated contact units given as a fifth embodiment of thepresent invention;

FIG. 6 b is a fragmentary longitudinal sectional view of the contactprobe provided with highly concentrated contact units

FIG. 7 a is a perspective view showing a socket given as a sixthembodiment of the present invention;

FIG. 7 b is a sectional view taken along line VIIb-VIIb of FIG. 7 a;

FIG. 8 a is a fragmentary longitudinal sectional view of a contact probeholder given as a seventh embodiment of the present invention;

FIG. 8 b is a view similar to FIG. 8 a showing the holder having aplastic layer formed over a high strength base plate;

FIG. 8 c is a view similar to FIG. 8 a showing an intermediate stage offabricating the holder; and

FIG. 9 is a schematic longitudinal sectional view of the conventionalcontact probe holder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic longitudinal sectional view of a contact probeusing a contact probe holder embodying the present invention, and FIG. 2is a sectional view taken along line II-II of FIG. 1. As shown in thedrawings, the illustrated contact probe 1 comprises a holder 2 in theform of a plate member, a plurality of contact units 3 which arearranged in two locations of the holder 2, and a circuit board 4 forelectrically connecting the contact units 3 with a testing device notshown in the drawings. The illustrated contact probe may be used fortesting LCD panels before completion as was the case with theconventional contact probe, and is adapted to be vertically moveable inthe drawings by using an arm 5 of an actuator to access the terminals(not shown in the drawings) of an LCD panel placed in a lower part asseen in the drawing for applying the contact probe 3 thereto for atesting purpose.

The holder 2 comprises a high strength base plate 6 made of a heatresistant and low thermal expansion coefficient metal alloy such asinvar and covar, and a holder hole forming member 7 made of plasticmaterial is filled or otherwise placed in an elongated opening 6 aprovided in a part of the high strength base plate 6. The high strengthmaterial for the base plate 6 may also be selected from semiconductormaterial, ceramic material and glass material depending on theparticular need. The plastic material may be selected from those whichare electrically highly insulating. In the illustrated high strengthbase plate 6, a layer 9 made of a same plastic material as the holderhole forming member 7 is placed over the overall surface of the highstrength base plate 6 as well as over the inner circumferential surfaceof the opening 6 a. This can be accomplished by first forming theplastic layer 9 in the form of film over the entire surface of the baseplate 6 and then filling the holder hole forming member 7 made of thesame material in the opening 6 a. The coating process that can be usedfor this purpose may be selected from calendar process, extrusion,dipping, spraying, spreading and electro-deposition. Conversely, one mayfirst fill the holder hole forming member 7 in the opening 6 a, and thenform the plastic layer 9 over the remaining surface of the base plate 6in the form of film. In either case, the holder hole forming member 7and plastic layer 9 integrally merge with each other. Further, theplastic layer 9 may also be formed at the same time as filling theopening 6 a with the holder hole forming member 7.

The contact units 3 in this contact probe 1 may be provided with any oneof a number of possible structures. In the illustrated embodiment, theholder hole forming member 7 placed in the opening 6 a is formed withlarge diameter holes 8 a and small diameter holes 8 b for the holderholes 8 in a coaxial manner axially through the thickness of the holderhole forming member 7. A compression coil spring 10 is coaxiallyreceived in each of the large diameter holes 8 a, and electroconductiveneedle members 11 and 12 are integrally attached to either axial end ofthe coil spring 10 by soldering, for instance.

Referring to FIG. 1, the upper needle member 11 is provided with acylindrical drum portion 8 a which is axially slidably received in thelarge diameter hole 8 a, and a pointed end which is directed upward. Thelower needle member 12 is provided a needle portion which is axiallyslidably received by the small diameter hole 8 b and a pointed end whichis directed downward. The lower needle member 12 is also provided with aflange portion which is received by the large diameter hole 8 a. Thecoil spring 10 is interposed between the flange portion and the upperneedle member 11, and the lower needle member 12 is prevented fromcoming off by the flange portion being engaged by a shoulder portiondefined between the large diameter hole 8 a and small diameter hole 8 b.

Referring to FIG. 1, the upper surface of the holder 2 is attached to anend of the circuit board 4 which may consist of a flexible printedcircuit board (FPC). The lower surface of the corresponding end of theFPC 4 is provided with terminal portions corresponding to the needlemembers 11. To the free end of the holder 2 remote from the endsupported by the arm 5 is fixedly attached another member consisting ofa fixed bracket 14. The corresponding end of the FPC 4 is fixedlyinterposed between the fixed bracket 14 and the corresponding part ofthe upper surface of the holder 2.

The upper open end of each large diameter hole 8 a is covered by theprinted circuit board 4, and the pointed ends of the needle members 11engage the corresponding terminal portions of the printed circuit board4 opposing the large diameter holes 8 a. By suitably adjusting thelength of each large diameter hole 8 a so that the corresponding coilspring 10 is compressed, the needle member 11 may be applied to thecorresponding terminal portion of the circuit board 4 with a suitableamount of resilient pressure. This ensures a favorable contact betweenthe needle member and terminal portion of the circuit board 4.

Because the holder holes 8 can be formed in the holder hole formingmember 7 after the holder hole forming member 7 is placed in position,the holder holes 8 can be formed in a desired configuration depending onthe particular model, and an improved versatility can be achieved asopposed to the case where a high strength base plate having a fixedconfiguration is used.

The holder is connected to the other member or the arm 5 by threadedbolts 15. In the illustrated embodiment, the arm 5 is provided with boltpassing holes 5 a and the corresponding part of the high strength baseplate 6 is provided with threaded holes (female threads) 16 forthreading the threaded bolts 15 thereinto so that the arm 5 and holder 2may be joined to each other. In this case, because the high strengthbase plate 6 is made of metallic material and the threaded holes 16 areformed in the metallic material, the fastening force achieved by thethreaded bolts 15 can be increased, and the holder 2 can be supported onthe arm 5 in a highly stable manner. Also, the threads would not bedamaged even after repeated assembling and disassembling of the twoparts, and this is beneficial for facilitating the maintenance andimproving the durability.

The threaded holes 17 for the threaded bolts 13 for securing the fixedbracket 14 to the holder 2 can also be formed in the high strength baseplate 6, and this allows the fixed bracket 14 to be firmly secured tothe holder 2 so that the circuit board 4 can be securely fixed simply byinterposing it between the holder 2 and fixed bracket 14. By forming thefixed bracket 14 with plastic material, the circuit board can beresiliently retained by making use of the resiliency of the plasticmaterial so that the circuit board 4 can be firmly secured without therisk of damaging it.

As shown in FIG. 2, the high strength base plate 6 is provided withholes 18 and 19 at suitable parts thereof for receiving locating pinsfor locating the arm 5 and fixed holder 14. These locating pin holes 18and 19 are formed in pin hole forming portions 21 and 22 that are placedin openings 6 b and 6 c provided in the high strength base plate 6. Thelocating pin holes 18 and 19 receive locating pins 23 and 24 that extendbetween the arm 5 and fixed holder 14. By forming the openings 6 b and 6c as elongated slots as illustrated in the drawing, the positions of thelocating pin holes 18 and 19 can be adjusted along the lengths of theopenings 6 b and 6 c so that the arrangement can be readily adapted tochanges in design.

In the electroconductive contact probe holder 2 described above, themetallic material that is used as the main material for the highstrength base plate 6 may be conveniently selected from those materialshaving a small coefficient of thermal expansion as compared with theplastic material that is used for the holder hole forming member 7. Whenthe plastic layer 9 in the illustrated embodiment is sufficiently thinas compared with the thickness of the high strength base plate 6, theholder 2 may be considered as virtually entirely made of metallicmaterial. Therefore, as opposed to the case where the holder is made ofa one-piece plastic member, the deformation of the holder that could beinduced owing to the change in temperature during use can be easilycontrolled. Also, the premature aging owing to the residual stressproduced as a result of machining of the holder can be avoided. Becausethe holder 2 can be given with a high level of rigidity, variousreinforcing measures (such as insert molding reinforcing plates) thatwould become necessary when the holder is substantially entirely made ofplastic material are not required. When electric insulation is required,an insulating plastic layer 9 may be provided. In this manner, thestructure is simplified, and the cost and time for manufacturing can beboth reduced.

When the holder hole forming member 7 and plastic layer 9 are bothintegrally formed with the high strength base plate 6, they can becontinually merged with each other so that the force for retaining theholder hole forming member 7 in the opening 6 a can be ensured. If thethickness of the plastic layer 9 is small, such a retaining force maynot be available. In such a case, a desired result can be achieved byusing different materials for the holder hole forming member 7 andplastic layer 9. Such an example is described in the following withreference to FIG. 3.

Referring to FIG. 3 a, an opening 6 a is formed in a high strengthsupport member 6 by etching, laser, blanking or other mechanical processso as to correspond to the individual chips in the wafer that is to betested. The high strength material for the support member 6 may consistof metallic material having a low coefficient of thermal expansion suchas invar and covar.

Referring to FIG. 3 b, relatively thin plastic layer 9 (tens or hundredsof μm thick) made of such material as insulating plastic material iscoated on the surface of the high strength support member 6 having theopenings 6 a. The possible methods of coating may include calendarprocess, extrusion, immersion, spraying, spreading and electrostaticdeposition. Referring to FIG. 3 c, a holder hole forming member 7 madeof plastic material or the like that is suitable for machining orotherwise forming the holder holes for the contact probe is filled intoeach of the openings 6 a. The plastic layer 9 demonstrates a highbonding strength with respect to the plastic material of the holder holeforming member 7. By providing such a plastic layer 9 on the innercircumferential surface of each opening 6 a, the high strength supportmember 6 and the plastic holder hole forming member 7 filled in theopenings 6 a can be firmly joined to each other. Referring to FIG. 3 d,a plurality of holder holes 8 (8 a and 8 b) corresponding in number tothe contact units for each individual chip are formed in the holder holeforming member 7.

Thus, even though the plastic layer 9 is extremely thin, an adequateadhesion (bonding or retaining force) can be ensured between the opening6 a and holder hole forming member 7 so that a lack of an adequatebonding force between the high strength base plate 6 and holder holeforming member 7 would not create a problem. Therefore, the metallicpart of the high strength base plate 6 prevents a change in the overalldimensions of the holder 2 while the holder hole forming member 7 forsupporting the contact units 3 may consist of material that is suitablefor machining and provided with a required lubricating property.According to the prior art, material which would not cause undesireddimensional changes even when exposed to significant changes intemperature is often unsuitable for machining and lacking in a requiredlubricating property. However, the present invention eliminates such acompromise in the selection of the material.

When a thin plastic layer 9 is coated over the surface of the holder,the thickness of the plastic layer can be made thinner than would bepossible if such a layer is formed by insert molding. In particular,even when the thickness of the holder is as small as 1 mm, a large partof the thickness of the holder is accounted for by the high strengthbase plate so that a high mechanical strength can be ensured even whenthe holder is thin. Therefore, this arrangement is highly suited for usein holders using thin base plate, and allow a thinner and large holderthan would be possible with the conventional arrangement to be achieved.

The contact probe described above was designed for testing LCD panels,but can also be used in other applications. For instance, the object tobe tested may consist of chips including highly densely populatedterminals. In such a case, because the terminals are highly denselyarranged and the adjacent needle members (coil springs) of the contactunits are located closely to one other, the thickness of the wallseparating the adjacent support holes 8 in the holder hole formingmember 7 becomes extremely thin. Therefore, the material for the holderhole forming member 7 is required to have a favorable electrostaticproperty. However, readily available plastic material having a favorableelectrostatic property tends to be poor in electric insulation.

However, a desired electric insulation can be ensured to the holder 2 byusing highly electrically insulating material for the plastic layer. Insuch a case, material having a favorable electrostatic property can beused for the holder hole forming member 7. Such an arrangement allows anelectrostatic property that meets the need of highly integrated devicesto be achieved. Thus, material that suits the particular need can beused for the holder hole forming member 7, and the application of thecontact probe can be expanded.

This is also applicable to contact probes for wafer level tests, and theholder for such an application is provided with a size comparable tothat of the wafer (200 to 300 mm in diameter). When the thickness ofsuch a holder is reduced to reduce the overall length of each contactunit, the holder is required to have a correspondingly high mechanicalstrength. The mechanical strength become greater as the proportion ofthe metallic or other high strength base plate in the total thicknessincreases, and the holder described above is suitable for such anapplication.

An insulating plastic layer 9 was formed over the surface of the highstrength base plate 6 in the above described embodiment, but may also beomitted if the high strength base plate 6 is electrically insulated withrespect to another component connected to the holder. If the connectingportion is not required to be insulated, the insulating plastic layer 9may not be formed over the surface of the high strength base plate 6. Insuch a case, the holder hole forming member 7 may be directly filledinto the opening 6 a.

As shown in FIG. 4 a, the openings 6 a can be formed in the highstrength base plate 6 by etching, and by conducting etching from bothdirections as indicated by the arrows in FIG. 4 a, a ridge 25 thatprojects radially inward in an axially middle part of the openings andcan serve as a means for preventing the dislodging of the holder holeforming portions 7 can be easily formed. This can be readilyaccomplished by using a base plate made from a silicon wafer, andanisotropically etching said inner circumferential surface of saidopening, and no special work is required.

By filling the holder hole forming portion 7 in the opening 6 a, arecess 7 a corresponding to the ridge 25 is formed in the holder holeforming portion 7 as shown in FIG. 4 b. Therefore, even when the holderhole forming portion 7 has shrunk over time, the engagement between theridge 25 and recess 7 a prevents the dislodging movement of the holderhole forming portion 7 (the axial direction of the opening 6 a), and theholder hole forming portion 7 can be retained in a reliable fashion.

The plastic layer 9 was directly formed over the surface of the highstrength base plate 6 in the foregoing embodiment, but it may also beformed over the surface of the high strength base plate 6 via aninsulating film 26 as illustrated in FIG. 5 which is similar to FIG. 1.In FIG. 5, the parts corresponding to those of the previous embodimentsare denoted with like numerals without repeating the description of suchparts.

Referring to FIG. 5, relatively thin film 26 (tens or hundreds of μmthick) made of such material as insulating plastic material is coated onthe surface of the high strength base plate 6 having the openings 6 a.The possible methods of coating may include calendar process, extrusion,immersion, spraying, spreading and electrostatic deposition. A holderhole forming member 7 made of plastic material or the like that issuitable for machining or otherwise forming the holder holes for thecontact units is filled into the opening 6 a. A layer made of the samematerial is placed over the part of the film 26 corresponding to thesurface of the high strength base plate 6.

By so doing, the insulation that is required when the high strength baseplate 6 is made of metallic material can be ensured, and the materialfor the holder hole forming member 7 can be selected from those havingdesirable properties but not particularly superior in electricinsulation. For instance, the material for the holder hole formingmember 7 may be provided with a favorable electrostatic property. Thefilm 26 may consist of material demonstrating a strong bonding forcewith respect to the plastic material, and the provision of film 26 madeof such material on the inner circumferential surface of the opening 6 aensures a strong attachment between the plastic holder hole formingmember 7 filled in the opening 6 a and high strength base plate 6.

The present invention is not limited in application to those for testingLCD panels before completion as described above in association with thedrawings, but may also be used in other testing and other devices usingcontact units. For instance, the present invention can be applied tosockets that are used for testing devices, package base boards formounting semiconductor chips and high density probes for wafer leveltests. In such applications also, the holder is desired to have a highmechanical strength, and the positional precision of the contact pointsare desired to be maintained over a prolonged period of time. Thepresent invention provides various benefits in such applications.

FIGS. 6 a and 6 b show such an example in the form of a highly denseprobe 27. FIG. 6 a is a overall perspective view of the contact probe,and FIG. 6 b is a fragmentary longitudinal sectional view thereof. Thisprobe 27 is designed for electrically testing a package base board formounting a semiconductor chip. The parts corresponding to those of theprevious embodiments are denoted with like numerals without repeatingthe description of such parts.

The needle members 12 for contacting the corresponding land portions onthe side of the chips are concentrated in a central part of the contactprobe 27, and a plurality of pushers 28 are arranged along the peripheryof the contact probe 27. Each pusher 28 is urged upward by a compressionspring, for instance, and controls the possible warping of the packagebase board (not shown in the drawing) that would be placed above duringtesting under the pressure from the contact probe 27 by resilientlyurging the peripheral part of the package base board.

The contact probe 27 is provided with a holder consisting of four layersof support members 29, 30, 31 and 32 as shown in the drawing. The uppersupport member 29 is provided with a plastic layer 9 placed over thesurface of a high strength base plate 6 via an insulating film 26 in asimilar manner as the example shown FIG. 5. The embodiment providessimilar advantages as those of the previous embodiments. The othersupport members 30, 31 and 32 may also consist of plastic base plates.The large diameter hole 8 a for receiving the coil spring 10 and theother needle member 11 are formed in the two intermediate supportmembers 30 and 31, and the lowermost base plate 32 is provided withexternal lead 33 s which are press fitted into holes formed in thesupport member 32 so as to correspond to the large diameter holes 8 a.The needle members 11 engage the end surfaces of the external leads 33.

FIGS. 7 a and 7 b show another example in the form of a socket. FIG. 7 ais an overall perspective view of the socket, and FIG. 7 b is afragmentary longitudinal sectional view thereof. This socket comprises asocket main body 34 and a base 35 in the form of a frame and serving asa retainer, and is used for mounting an IC chip on a printed circuitboard, for instance. The socket main body 34 may be similar in structureto the contact probe shown in FIG. 6.

Referring to FIG. 7 b, the socket main body 34 is fixedly attached to acircuit board consisting of a tester board 36 in this case via the base35. A circuit pattern 36 a is formed on the tester board 36corresponding to the needle members 11 of the socket main body so thatthe needle members 11 may engage the corresponding terminal portions ofthe circuit pattern 36 a.

The base 35 is provided with an inverted L-shaped cross section, and isadapted to surround and cover the peripheral part of the socket mainbody 34 as shown in the drawing. The base 35 is located with respect tothe tester board 36 by locator pins not shown in the drawing, and isfixedly attached to the tester board 36 by threaded bolts now shown inthe drawing. The peripheral part of the socket main body 34 is attachedto the inwardly directed flange portion 35 a of the base 35 that coversthe peripheral part of the socket main body 34 by threaded bolts 38.

The base 35 is formed by placing a plastic layer 9 over the surface of ahigh strength base plate 6 via an insulating film 26 similarly as theprevious embodiment, and the overall shape of the base 35 is defined bythe plastic material of the plastic layer 9. This embodiment providessimilar advantages as the previous embodiments.

In the illustrated embodiment, the threaded holes 35 b for joining thebase 35 with the tester board 36 by using threaded bolts and thethreaded holes 35 c for joining the base 35 with the socket main body 34by using threaded bolts are all formed in the high strength base plate6. This ensures a strong force for attachment, and allows the socketmain body 34 to be attached to the tester board 36 at high precision andin a highly rigid manner. When such a strong force for attachment is notrequired, the threaded holes 35 b and 35 c may not be provided in thehigh strength base plate 6.

FIGS. 8 a and 8 b show a holder suitable for use in a contact probe fortesting LCD panels similarly as the embodiment illustrated in FIGS. 1and 3. The parts corresponding to those of the previous embodiment aredenoted with like numerals without repeating the description of suchparts.

A high strength base plate 6 made of a heat resistant metallic materialhaving a low coefficient of thermal expansion such is invar and covar isprovided with an opening 6 a in the form of a slot, and a plastic layer9 made of highly insulating plastic material is deposited on the surfaceof the base plate in the form of film. The opening 6 a receives a holderhole forming member 60 therein. A thin-walled portion 6 b of the baseplate 6 extends along a side of the opening 6 a, and a correspondingthin-walled portion 60 a of the holder hole forming member 60 is placedover the thin-walled portion 6 b of the base plate 6. Threaded bolts 16are passed through through-holes formed in the thin-walled portion 60 aof the holder hole forming member 60, and are threaded intocorresponding threaded holes formed in the thin-walled portion 6 b ofthe base plate 6 to firmly join these two parts together.

The holder hole forming member 60 and plastic layer 9 are made ofdifferent plastic materials, and the plastic layer 9 contributes to afirm bonding between the holder hole forming member 60 and the baseplate 6 and demonstrates a high level of insulation. The base plate 6 isprovided with threaded holes 64 and locating holes 63 for fixedlysecuring a fixed bracket or the like to the holder.

FIG. 8 c shows an intermediate stage of fabricating the holder shown inFIGS. 8 a and 8 b. First of all, the holder hole forming member 60 isfixed in position inside the opening 6 a of the base plate 6 having theplastic layer 9 formed thereon by using the threaded bolts 16. For thispurpose, locating holes are provided in the two thin-walled portions 60a and 6 b, and only the locating holes 62 formed in the thin-walledportion 60 a of the holder hole forming member 60 are shown in FIG. 8 a.Thereafter, the same material as the plastic layer 9 is deposited overthe entire surface of the holder not only to cover the surfaces of boththe base plate 6 and holder hole forming member 60 but also to fill thegaps between them. The surface of the plastic layer 9 now given with anincreased thickness is machined or ground until the holder hole formingmember 60 is exposed (as indicated by the broken lines 70 in FIG. 8 c.

Thus, according to the present invention, the base plate of the holdermay be made of metallic material having a low coefficient of thermalexpansion. In such a case, because the holder can be considered as beingessentially made of metallic material, dimensional changes owing tochanges in temperature during testing (tests under high temperatureconditions) can be controlled easily as compared with the case where theholder is entirely made of plastic material. Dimensional changes due toaging compounded by residual stress can be avoided. Therefore, even whenthe terminals of the chip or the like that are to be accessed aredensely arranged, an adequate level of positional precision can bemaintained in the pitch of the corresponding contact units withoutregard to the surrounding environment and the service period, and testscan be conducted in a stable manner over an extended period of time.

By forming film on the inner circumferential surface of the opening toensure a strong bonding force with respect to the holder hole formingmember, a high bonding force is provided between the holder hole formingmember and the opening, and the contact probe can be formed as a highlyintegral unit.

When the threaded holes for joining the holder to another member areprovided in the high strength base plate, the mechanical strength of thethread is increased as compared with that formed in a plastic member,and the fastening force of the threaded bolts can be increased.Therefore, the holder can be firmly joined to the other member. Also,even if the holder is assembled and disassembled repeatedly, the threadwould not be damaged, and the maintenance of the contact probe isfacilitated.

The holder hole forming member may consist of plastic material whichdoes not tend to generate static electricity, and the part of thesurface of the high strength base plate that requires insulation may beprovided with an insulating film. In this manner, even when theelectrostatic property is required to be considered owing to the highlydense population of the terminals of the chip or other object to betested, the holder hole forming member may be made from plastic materialhaving a favorable electrostatic property as the insulating film makesup for the deficiency of the material of the holder hole forming membermay have in electric insulation.

By virtue of the laminated structure including film and materialsuitable for forming holder holes, the masking that would be necessarywhen material suitable for forming holder holes is simply filled intothe opening is not required, and the work efficiency can be improved. Iffilm consisting of insulating plastic material is coated over thesurface of the base plate, and the material suitable for forming holderholes that is placed over the film is electrically insulating, theoverall insulating property can be improved owing to the provision ofthe two layers of insulating material. Therefore, the thickness of thefilm and layer can be reduced without impairing the insulatingperformance, and the reduced thickness of the film and layer allows thethickness of the holder to be minimized.

Although the present invention has been described in terms of preferredembodiments thereof, it is obvious to a person skilled in the art thatvarious alterations and modifications are possible without departingfrom the scope of the present invention which is set forth in theappended claims.

1. An electroconductive contact probe holder for supporting a pluralityof contact units for contacting an object, comprising: a base plate madeof a first material and provided with an opening therein; and film madeof a second material and deposited on a surface of said base plate so asto cover at least an inner circumferential surface of said opening; aholder hole forming member made of a third material and filled in saidopening substantially without extending outside said opening; aplurality of holder holes being passed across a thickness of said holderhole forming member each for receiving a contact unit therein.
 2. Anelectroconductive contact probe holder according to claim 1, whereinsaid first material comprises a member selected from a group consistingof metallic material, semiconductor material, ceramic material and glassmaterial.
 3. An electroconductive contact probe holder according toclaim 1, wherein said second and third materials comprise a same ordifferent plastic materials.
 4. An electroconductive contact probeholder according to claim 1, wherein said film is formed substantiallyover an entire surface of said base plate.
 5. An electroconductivecontact probe holder according to claim 1, wherein said film is made ofmaterial that promotes bonding between said holder hole forming memberand said base plate.
 6. An electroconductive contact probe holderaccording to claim 1, wherein said film is made of material thatpromotes electric insulation between said holder hole forming member andsaid base plate.
 7. An electroconductive contact probe holder accordingto claim 1, wherein said second material produces more electricallyinsulating than said third material, and said third material producesless static electricity that said second material.
 8. Anelectroconductive contact probe holder according to claim 1, wherein anengagement feature is formed on an inner circumferential surface of saidopening.
 9. An electroconductive contact probe holder according to claim8, wherein said base plate is made of a silicon wafer and the engagementfeature comprises an inwardly directed ridge formed by anisotropicallyetching said inner circumferential surface of said opening.
 10. Anelectroconductive contact probe holder according to claim 1, whereinsaid base plate is provided with a threaded hole for joining said holderwith another member.
 11. An electroconductive contact probe holderaccording to claim 1, wherein said base plate is provided with alocating hole for locating said holder with respect to another member.12. An electroconductive contact probe holder according to claim 1,wherein said holder hole forming member is provided with a locating holefor locating said holder with respect to another member.
 13. Anelectroconductive contact probe holder according to claim 1, whereinsaid film is formed substantially only on an inner circumferentialsurface of said opening.
 14. An electroconductive contact probe holderaccording to claim 14, wherein said holder hole forming member isfixedly secured in said opening with a threaded bolt.
 15. Anelectroconductive contact probe holder according to claim 14, whereinsaid film is deposited on said substrate with said holder hole formingmember placed in said opening.
 16. An electroconductive contact probeholder according to claim 15, wherein a surface of said film ismachined/ground.